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stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Thu Jul 23, 2009 11:21 am    Post subject: Sanyo HT30744 Reply with quote

this tv was working fine until being moved via a uhaul truck now when you plug it in and turn it on, you can hear it power up and a little green flicker on the screen then it goes blank without the picture coming fully into view. i have fixed several different types of electronic equipment but never have attempted anything on a tv. if you guys have any suggestions as to what might be the cause of this or possibly even a simple fix (if there is such a thing) or a website with information that i could study pertaining to televisions it would be greatly appreciated. any input is welcome.

thanks,
-steve
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JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Thu Jul 23, 2009 12:40 pm    Post subject: Reply with quote

Start with a good visual inspection. Since the set was working before being moved, perhaps something was jostled loose? Wink

Last edited by JTS1957 on Thu Jul 23, 2009 9:42 pm; edited 1 time in total
stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Thu Jul 23, 2009 2:43 pm    Post subject: Reply with quote

JTS1957 wrote:
Strat with a good visual inspection. Since the set was working before being moved, perhaps something was jostled loose? Wink


i have thought of that, that is when i decided to crack the case open and take a look, but like i said i have never worked on a tv before so i am lost as to what i am looking at. i have checked all the cables that are easily accessible and everything seems to be seated fully. I have read that there are several capacitors that carry a significant amount of current that would be deadly if discharged, so i am hesitant to "play" around in there. is there a proper way to check the tube to see if it might be cracked or damaged?
stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Thu Jul 23, 2009 6:59 pm    Post subject: Reply with quote

would it be possible that degaussing the set would potentially fix this problem, not sure what is causing it, just curious. what would be the proper way to degauss a set? when the set is plugged in it makes a sound like it is coming on before the power button is actually pushed (not sure if this is normal) then when the power button is pushed it emits a flash of colors across the screen then goes blank and you can see a faint bit of color "swirling" around in the middle of the screen in about a 1-1.5" diameter circle.
JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Thu Jul 23, 2009 9:48 pm    Post subject: Reply with quote

Doesn't sound like a degaussing symptom. Should have an automatic degaussing circuit that functions each time set is started (if working properly).
Should also check for cracked circuit boards. Set wasn't dropped or something fell onto it?
Capacitors: "Ouch" Yes - "Deadly" Not likely.
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stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Fri Jul 24, 2009 1:56 am    Post subject: Reply with quote

i should be able to "easily" test caps with a convenient multimeter, but where would i start? are there certain caps that would be the first to go. as for being dropped not that i know of, maybe some bumps in the road during transportation? i know its hard to decipher a problem without the set actually being in front of you, just trying to figure out where i would start, to at least find out where the problem lies, then go about fixing it. thank you for your replies. i found a service manual on this set and yes it does have an automatic degaussing circuit, as for working properly im not sure of, i have not heard any 'boing' sound as if it was degaussing when the set is powered up though.
JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Fri Jul 24, 2009 3:25 am    Post subject: Reply with quote

stevetxbc wrote:
...but where would i start? ...
At the beginning. Smile

No Picture - ?No Sound?
Is this your personal TV? Are you used to the way the set powers up/down in regards the flash of colors / "swirling?" (Is "Normal"/"Abnormal"?) I've also pulled up a Service manual for this set.
Almost sounds like the set is powered "On" as the cord is plugged in, then when you hit the power button the set turns "Off" and you get the color "swirling." If so, ignore the power switch and see if the set indeed turns on when plugged in / turns off when unplugged?
stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Fri Jul 24, 2009 11:01 am    Post subject: Reply with quote

once again thank you for your time and help.
now this was my fathers tv but i took it off his hands as a project hoping to try to fix it and learn a few things about tvs in the process seems like it would be something i would like to get into, seems complicated at first (most things electronic do) but i know once i study it things will get easier, okay so i was plugging and unplugging the set before i actually saw your latest post and i was thinking the exact same thing about it powering on when being plugged in then powering off when the button is pushed. i was reading on page 18 of the service manual and it states that if there is a "short" or low voltage supply the CPU will turn the set off withing 1.5 seconds that also seems to be happening so im hoping it could be a resistor or possibly a bad cap. it also says that if there is a failure 3 times in a row the cpu will cease to function and the power button will not operate, this also happens. i was reading elsewhere on the web about a set different than the one i have about a non powering failure and he is testing from the HOT to the collector, could this be a test i should perform? and (my noobiness again) where would the HOT be located on this set looking at the diagrams in the service manual (board number)?


Last edited by stevetxbc on Fri Jul 24, 2009 1:06 pm; edited 1 time in total
JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Fri Jul 24, 2009 1:04 pm    Post subject: Reply with quote

So CAN you control the turning ON/OFF of the set JUST BY plugging/unplugging the cord? YES or NO? Exclamation HAS/DOES'NT Have SOUND?
You say you see colors/light/swirls on the face of the tube. That means you Do have High voltage. Which means that HOT should be O.K.
stevetxbc



Joined: 22 Jul 2009
Posts: 7
Location: Texas

PostPosted: Fri Jul 24, 2009 1:11 pm    Post subject: Reply with quote

it sounds as though it powers up when plugged in and powers off when unplugged yes. as far as sound i cannot tell i do not hear anything static or the like. i tried turning up the volume before and after pushing the power button and still do not hear anything.
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